The subject invention generally relates to a steering column assembly for a vehicle, and more specifically to a collapsible steering column assembly having an energy absorption system for absorbing energy during collapse of the steering column assembly.
A vehicle steering column assembly may include an energy absorption system for dissipating kinetic energy during an impact between a vehicle occupant and the steering column. An energy absorption system may thereby reduce the likelihood or severity of an injury to the vehicle operator in the event of a collision involving the vehicle. For example, in a front end collision interrupting the forward progress of the vehicle, a vehicle occupant impacting the steering wheel may impose a column compression force upon the steering column. If the column compression force is of sufficient magnitude, a collapse of the steering column along its longitudinal axis may be encountered.
An energy absorption system may be implemented and configured so as to deliver a collapse resistance force that tends to oppose the column compression force. To overcome the collapse resistance force, an input of work (i.e., energy) is required as the steering column collapses, and the steering column is thus able to “absorb” the energy (i.e., work) in overcoming the collapse resistance force as that energy is expended throughout the collapse stroke. This release of energy over the finite period of time required to traverse the collapse stroke, as apposed to the instantaneous release of energy that would be associated with an impact with a rigid body, results in a substantial decrease in the magnitude of the impulse encountered by the vehicle occupant in the event of a vehicle collision.
As one skilled in the art will appreciate, a collapsible steering column assembly may include a housing configured to translate linearly through a collapse stroke. As soon as the steering column has been released from its relatively fixed position with respect to the vehicle, energy absorption during the collapse stroke becomes feasible. Accordingly, when a vehicle occupant first impacts the steering wheel and exerts a sufficient break-away force on the steering column (or as soon as a collision event has been detected and the steering column is automatically released), a force exerted by the occupant upon the steering column (i.e., column compression force) is available to perform work. One skilled in the art will appreciate that the force exerted by the occupant on the steering column is related to not only the rate at which the column mass is accelerated by the force exerted by the occupant, but also to the force that resists the collapse of the steering column. This collapse resistance force may be created and controlled by an energy absorption system, which is designed to dissipate a portion of the occupant's kinetic energy.
In general, the collapse resistance force may be created through a variety of means, including by causing a strap to be drawn through or over a path or surface of resistance as the housing of the collapsible steering column assembly translates through the collapse stroke. As the strap passes through the path or over the surface, the strap may be deformed, friction may be encountered between the strap and the surface, and/or other mechanisms may be employed for resisting the relative movement between the strap and the surface.
Typically, a collapsible steering column assembly includes a column jacket having two ends; a steering wheel end and an output end. A bracket is mounted to the column jacket for attaching the column jacket to the vehicle, and one or more release modules interconnect the bracket to the vehicle. The release modules may be configured to release the interconnection between the column jacket and the vehicle upon the occurrence of a predetermined event, such as a vehicle collision. A release module may include a bore, through which a fastener, such as a bolt, passes through to mechanically couple the release module to the vehicle. A strap may be connected to the bracket for movement with the bracket and the column jacket during the collapse stroke. The strap passes through a deformation device, such as an anvil that defines a strap channel. Thus, during the collapse stroke, the strap is deformed or otherwise caused to encounter a collapse resistance force imparted by the anvil. A deformation channel may be incorporated into the release module.
Accordingly, it is desirable to have a steering column assembly with an energy absorption system that can facilitate reliable, cost-effective control over the collapse resistance force. It would also be advantageous to have a steering column assembly with an energy absorption system that provides for variations in the collapse resistance force at different stages of a collapse stroke.